A sixth-grader is shot in the leg by an 11-year-old student in the Redland. A fifth-grader with special needs shows up to a Doral K-8 with a loaded Smith & Wesson. A 13-year-old girl is shot and killed aboard a private school bus by a boy with a gun tucked in his backpack.

The unusual spate of gun-related incidents closed out the 2012-2013 school year in Miami-Dade County, amid a still-simmering debate in the wake of the mass shooting at Sandy Hook Elementary in Newtown, Conn.

Each incident raised the same question: How safe are our children from gun violence in school?

As the summer began, Miami Herald education writer David Smiley set out on a fact-finding mission. “Most of the time you don’t hear if a gun is found in a school,” he said. “We wanted to know ‘What are local schools really dealing with?’”

Smiley requested all police reports from 2009 to 2012 involving gun-related incidents at all public schools in Miami-Dade and Broward, the fourth and sixth-largest school districts in the country, respectively. It took months to gather the information, then sift through the 200 cases to hone in on the incidents that involved guns inside schools or on school property.

It was a painstaking endeavor, a first-time effort to get a full picture of the problem locally.

An interactive map created by Herald multimedia producer Lazaro Gamio plots each of the 137 incidents at each of the 80 schools in both Miami-Dade and Broward counties. The map, at http://www.miamiherald.com/static/media/projects/guns_school/, includes every school, including the majority which reported no incidents, for a true side-by-side comparison. The size of the school’s red circle grows with the number of incidents and contains a detailed report on each case.

Smiley’s reporting found that 75 percent of the schools in Miami-Dade did not have a single gun-related incident during the last four years, a lower rate than some smaller Florida school districts. However, of the six schools that had five or more cases, all are clustered in Miami and Miami Gardens.

”Generally they are doing a good job of keeping guns out of school,” he said. “And when they do find their way into schools, they have a good safety net of student and parent tipsters and aware teachers and police.”

Take the incident on Sept. 28, 2010, at American Senior High School in Northwest Miami-Dade, where a teacher overheard a student conversation about bringing a gun to school. The teacher reported it to police who searched the student and found a .22 caliber gun — and 109 bullets. The student said he was trying to sell them.

“They are trying to do everything they can to keep guns out of school without turning schools into a vault,” Smiley said.